Advances in multilevel approaches to understanding the epidemiology and prevention of sexually transmitted infections and HIV: an overview

A novel simulation-based analysis of a stochastic HIV model with the time delay using high order spectral collocation technique

The economic impact of Human Immunodeficiency Virus (HIV) goes beyond individual levels and it has a significant influence on communities and nations worldwide. Studying the transmission patterns in HIV dynamics is crucial for understanding the tracking behavior and informing policymakers about the possible control of this viral infection. Various approaches have been adopted to explore how the virus interacts with the immune system. Models involving differential equations with delays have become prevalent across various scientific and technical domains over the past few decades. In this study, we present a novel mathematical model comprising a system of delay differential equations to describe the dynamics of intramural HIV infection. The model characterizes three distinct cell sub-populations and the HIV virus. By incorporating time delay between the viral entry into target cells and the subsequent production of new virions, our model provides a comprehensive understanding of the infection process. Our study focuses on investigating the stability of two crucial equilibrium states the infection-free and endemic equilibriums. To analyze the infection-free equilibrium, we utilize the LaSalle invariance principle. Further, we prove that if reproduction is less than unity, the disease free equilibrium is locally and globally asymptotically stable. To ensure numerical accuracy and preservation of essential properties from the continuous mathematical model, we use a spectral scheme having a higher-order accuracy. This scheme effectively captures the underlying dynamics and enables efficient numerical simulations.

Trends and projections in sexually transmitted infections in people aged 45 years and older in England: analysis of national surveillance data

AIMS

We describe the epidemiology of sexually transmitted infections (STIs) and HIV in people aged ⩾45 years in England and provide future projections about the burden of STIs in this age group.

METHODS

Analysis of national surveillance data in England from 2014 to 2019 for chlamydia, gonorrhoea, herpes, syphilis, anogenital warts and HIV was carried out. Time trends were assessed by the Poisson regression and reported using incidence rate ratios (IRRs). Two scenarios were modelled to predict the number of new STI diagnoses and associated costs in 2040.

RESULTS

In 2019, there were 37,692 new STI diagnoses in people ⩾45 years in England. Between 2014 and 2019, there was a significant increase in the rate of new STI diagnoses in men (IRR = 1.05, p = .05) and those aged 45-64 years (IRR = 1.04, p = .05). Absolute numbers of new STI diagnoses in men who have sex with men increased by 76% between 2014 and 2019 (IRR = 1.15, p < .001). In adults aged ⩾50 years, the number of episodes of care for HIV increased over time (age = 50-64 years, IRR = 1.10; age = 65+ years, IRR = 1.13; p <.001). The modelled scenarios predicted an increase in STI diagnoses and costs in older people by 2040.

CONCLUSION

STI rates in England are increasing in people aged ⩾45 years. The population is ageing and older people will contribute an increasing burden to STI costs if this trend continues. The reasons for this trend are not fully understood and further longitudinal epidemiological research is needed. Sexual health promotion campaigns and healthcare interventions targeted at older people should be prioritised.

Getting to zero HIV/AIDS in sub-Saharan Africa: Understanding perceptions of locals using the social determinants of health framework

This study explored a community perception of the facilitators and inhibitors of Getting to Zero (GTZ) in rural Zambia, sub-Saharan Africa. Data were collected in 2017. We use the Social Determinants of Health framework to guide organisation of key themes emerging from semistructured, focus group interviews with community members (N = 52). Data were analysed through an iterative descriptive/thematic approach which allowed for the highlighting of key themes. Emerging themes point to the significance of (a) individual, (b) sociocultural, (c) environmental and (d) economic factors, for example, treatment adherence, gender norms, food security and access to health care as important in GTZ. Implications for policy, practise and scholarship are suggested.

Social and behavioural research prospects for sexually transmissible infection prevention in the era of advances in biomedical approaches

In the past two decades, major advances in biomedical intervention approaches to prevent HIV and many sexually transmissible infections (STIs) have shown great promise. However, challenges to prevention remain in the area of achieving population-level impact for biomedical prevention approaches. In this paper we address what social and behavioural research approaches can contribute beyond well-known behaviour change and counselling interventions. We organise work into five areas. Adherence and disinhibition research is primarily into individual-level constructs pertaining to maximising intervention effectiveness. Coverage research represents a population-level construct germane to maximising efficient prioritisation for prevention. Research covering social determinants, a second population-level construct, contributes to both prioritisation and effectiveness. Finally, disparities and social inequities need to be incorporated into prevention, given the pervasive and persistent disparities found in rates of HIV and STIs and in their antecedents.

Does Intense Sexually Transmitted Infection Screening Cause or Prevent Antimicrobial Resistance in Sexually Transmitted Infections? It Depends on One's Underlying Epistemology. A Viewpoint

Certain authors argue that intensive sexually transmitted infection (STI) screening is a crucial way to reduce STI prevalence and prevent the emergence and spread of antimicrobial resistance (AMR) in STIs. Others argue the opposite: intense screening in high STI prevalence populations has little effect on prevalence and is likely to select for AMR. In this viewpoint, I argue that these radical differences in outlook stem, in part, from different conceptual frameworks of the determinants of STI prevalence and AMR. In the absence of strong evidence from randomized controlled trials, our brains interpret the weaker evidence from other sources in different ways, depending on our underlying epistemologies. To illustrate the argument, I contrast a predominantly biomedical individualist conceptual framework with a more ecological conceptual framework. I argue that if one's conceptual framework is based in biomedical individualism, then one is more likely to think that screening reduces STI prevalence and less likely to appreciate the connection between screening, antimicrobial exposure, and AMR than perspectives grounded in ecological frameworks.

Implementation of HIV Interventions Into Faith-Based Organizations: Models and Methodological Considerations

BACKGROUND

Implementation of evidence-based interventions aimed at reducing and treating HIV can have a wider spread if funneled through faith-based organizations. However, there is a paucity of frameworks or process models aimed at providing the best practices to implement HIV interventions into faith-based community organizations.

SETTING

Implementation framework and process model for African American faith settings.

RESULTS

Presented here is a systems multilevel implementation framework and implementation process model for integrating HIV interventions into faith-based organizations. We conclude with presentation of key methodological considerations and recommendations and discuss strategies for moving implementation science forward in faith-based organizations.

CONCLUSION

Because of their key role in the African American community, faith-based settings must be engaged in implementing evidence-based HIV interventions. Through use of a multilevel systems framework and process model, the methods and approaches of implementation science can be leveraged to encourage the spread of HIV interventions in the African American community.

Differential sexual network connectivity offers a parsimonious explanation for population-level variations in the prevalence of bacterial vaginosis: a data-driven, model-supported hypothesis

BACKGROUND

The prevalence of bacterial vaginosis (BV) and vaginal microbiota types varies dramatically between different populations around the world. Understanding what underpins these differences is important, as high-diversity microbiotas associated with BV are implicated in adverse pregnancy outcomes and enhanced susceptibility to and transmission of sexually transmitted infections.

MAIN TEXT

We hypothesize that these variations in the vaginal microbiota can, in part, be explained by variations in the connectivity of sexual networks. We argue: 1) Couple-level data suggest that BV-associated bacteria can be sexually transmitted and hence high sexual network connectivity would be expected to promote the spread of BV-associated bacteria. Epidemiological studies have found positive associations between indicators of network connectivity and the prevalence of BV; 2) The relationship between BV prevalence and STI incidence/prevalence can be parsimoniously explained by differential network connectivity; 3) Studies from other mammals are generally supportive of the association between network connectivity and high-diversity vaginal microbiota.

CONCLUSION

To test this hypothesis, we propose a combination of empirical and simulation-based study designs.

The Black-White Disparity in Sexually Transmitted Diseases During Pregnancy: How Do Racial Segregation and Income Inequality Matter?

BACKGROUND

We investigate the roles of residential racial segregation and income inequality for the black-white disparity in acquiring sexually transmitted diseases (STD) during pregnancy in a multilevel framework.

METHODS

The analytic sample consisted of non-Hispanic white (n = 79,271) and non-Hispanic black (n = 17,669) mothers from 2012 population birth data from Pennsylvania. We used the 2009 to 2013 American Community Survey for neighborhood characteristics of mothers; we used multilevel models.

RESULTS

First, neighborhood-level factors are important for understanding this disparity because racial segregation and income inequality are significantly associated with acquiring STD during pregnancy, regardless of race. Second, racial segregation moderates the relationships between race/ethnicity and the acquisition of STD during pregnancy. White mothers are more vulnerable to neighborhood segregation than black mothers, and black mothers are less likely to acquire STD during pregnancy than white mothers if they reside with co-ethnics. Third, mothers residing in the most socioeconomically disadvantaged neighborhoods-as indicated by both absolute and relative measures of income inequality-have the highest odds of acquiring STD during pregnancy, regardless of race.

CONCLUSIONS

Neighborhood-level segregation and income inequality are important for understanding the acquisition of STDs during pregnancy. Our findings have important implications for future research and for place-specific prevention and intervention to reduce the racial disparity in STD during pregnancy.

HIV prevalence by ethnic group covaries with prevalence of herpes simplex virus-2 and high-risk sex in Uganda: An ecological study

Background

HIV prevalence varies from 1.7% to 14.8% between ethnic groups in Uganda. Understanding the factors responsible for this heterogeneity in HIV spread may guide prevention efforts.

Methods

We evaluated the relationship between HIV prevalence by ethnic group and a range of risk factors as well as the prevalence of herpes simplex virus-2 (HSV-2), syphilis and symptomatic STIs in the 2004/2005 Uganda HIV/AIDS Sero-Behavioural Survey—a two stage, nationally representative, population based survey of 15–59-year-olds. Spearman’s correlation was used to assess the relationship between HIV prevalence and each variable.

Results

There was a positive association between HIV prevalence and HSV-2, symptomatic STIs and high-risk sex (sex with a non-cohabiting, non-marital partner) for women. Non-significant positive associations were present between HIV and high-risk sex for men and lifetime number of partners for men and women.

Conclusion

Variation in sexual behavior may contribute to the variations in HIV, HSV-2 and other STI prevalence by ethnic group in Uganda. Further work is necessary to delineate which combinations of risk factors determine differential STI spread in Uganda.

A Therapeutic Perspective of Living with Human Immunodeficiency Virus/AIDS in 2017

Patients with human immunodeficiency virus (HIV)/AIDS live a far different life today compared with those who were infected in the 1980s and 1990s. Antiretroviral therapy has evolved from a once poorly tolerated, heavy pill burden to the availability of many once-daily single-tablet regimens. The improvements in therapy have necessitated the need to be cognizant of comorbidities as well as drug-drug interactions. Despite the tremendous advances in therapy, newer therapies are in the pipeline and continue to emerge, making care for patients burdened by HIV perhaps easier than it has ever been.

Sex Work as an Emerging Risk Factor for Human Immunodeficiency Virus Seroconversion Among People who Inject Drugs in the SurvUDI Network

BACKGROUND

Recent analyses have shown an emerging positive association between sex work and human immunodeficiency virus (HIV) incidence among people who inject drugs (PWIDs) in the SurvUDI network.

METHODS

Participants who had injected in the past 6 months were recruited across the Province of Quebec and in the city of Ottawa, mainly in harm reduction programs. They completed a questionnaire and provided gingival exudate for HIV antibody testing. The associations with HIV seroconversion were tested with a Cox proportional hazard model using time-dependent covariables including the main variable of interest, sexual activity (sex work; no sex work; sexually inactive). The final model included significant variables and confounders of the associations with sexual activity.

RESULTS

Seventy-two HIV seroconversions were observed during 5239.2 person-years (py) of follow-up (incidence rates: total = 1.4/100 py; 95% confidence interval [CI], 1.1-1.7; sex work = 2.5/100 py; 95% CI, 1.5-3.6; no sex work = 0.8/100 py; 95% CI, 0.5-1.2; sexually inactive = 1.8/100 py; 95% CI, 1.1-2.5). In the final multivariate model, HIV incidence was significantly associated with sexual activity (sex work: adjusted hazard ratio [AHR], 2.19; 95% CI, 1.13-4.25; sexually inactive: AHR, 1.62; 95% CI, 0.92-2.88), and injection with a needle/syringe used by someone else (AHR, 2.84; 95% CI, 1.73-4.66).

CONCLUSIONS

Sex work is independently associated with HIV incidence among PWIDs. At the other end of the spectrum of sexual activity, sexually inactive PWIDs have a higher HIV incidence rate, likely due to more profound dependence leading to increased vulnerabilities, which may include mental illness, poverty, and social exclusion. Further studies are needed to understand whether the association between sex work and HIV is related to sexual transmission or other vulnerability factors.

International migration from non-endemic settings as a protective factor for HIV/STI risk among female sex workers in Vancouver, Canada

Given heterogeneous evidence regarding the impacts of migration on HIV/sexually transmitted infections (STIs) among female sex workers (FSWs), we explored factors associated with international migration among FSWs in Vancouver, Canada. We draw on baseline questionnaire and HIV/STI testing data from a community-based cohort, AESHA, from 2010-2012. Logistic regression identified correlates of international migration. Of 650 FSWs, 163 (25.1%) were international migrants, who primarily worked in formal indoor establishments. HIV/STI prevalence was lower among migrants than Canadian-born women (5.5 vs. 25.9%). In multivariate analysis, international migration was positively associated with completing high school, supporting dependents, and paying a third party, and negatively associated with HIV, injecting drugs and inconsistent condom use with clients. Although migrants experience lower workplace harms and HIV risk than Canadian-born women, they face concerning levels of violence, police harassment, and HIV/STIs. Research exploring structural and socio-cultural factors shaping risk mitigation and migrants' access to support remains needed.

HIV Community Viral Load and Factors Associated With Elevated Viremia Among a Community-Based Sample of Men Who Have Sex With Men in Vancouver, Canada

BACKGROUND

We developed estimates of community viral load (VL) and risk factors for unsuppressed VL from a cross-sectional study of men who have sex with men (MSM) in Vancouver, Canada.

METHODS

MSM were recruited from February 25, 2012 to February 28, 2014 using respondent-driven sampling (RDS). Participants completed a computer-assisted self-interview questionnaire and a nurse-administered point-of-care HIV test. For HIV-positive participants, we conducted VL and CD4 cell counts. We used RDS-weighted analysis to obtain population estimates of key variables and multivariable logistic regression to examine factors associated with having a VL of ≥200 copies per milliliter among HIV-positive participants.

RESULTS

We recruited 719 participants, of whom 119 (16.6%) were seeds. Our estimate of the population prevalence of HIV was 23.4% [95% confidence interval (CI): 15.8% to 31.0%] after RDS adjustments. We estimated that 18.6% (95% CI: 8.8% to 30.4%) of HIV-positive MSM in Vancouver had a VL of ≥200 copies per milliliter. Having an unsuppressed VL was associated with non-white ethnicity [adjusted odds ratio (AOR) = 4.34; 95% CI: 1.67 to 11.1], an annual income of <$15,000 CAD (AOR = 6.43; 95% CI: 2.08 to 19.9), using gamma-hydroxy butyrate in the previous 6 months (AOR = 4.85; 95% CI: 1.79 to 13.2), unprotected anal intercourse with a known HIV-negative or an unknown serostatus partner (AOR = 3.13; 95% CI: 1.10 to 8.90), and disclosing one's HIV serostatus ≥50% of the time (AOR = 7.04; 95% CI: 1.01 to 49.1).

CONCLUSION

Despite a high prevalence of HIV, we estimated that a small proportion of HIV-positive MSM have undiagnosed HIV and unsuppressed VL. Our results highlight the importance of continued work to address health inequities using a framework based on social determinants of health.

Incidence and Predictors of HIV and Sexually Transmitted Infections Among Female Sex Workers and Their Intimate Male Partners in Northern Mexico: A Longitudinal, Multilevel Study

Preventing human immunodeficiency virus (HIV) infection and other sexually transmitted infections (STIs) requires an understanding of sexual relationship factors beyond the individual level. We estimated HIV/STI incidence and identified time-varying predictors of STI acquisition in a prospective cohort study of female sex workers and their intimate (noncommercial) male partners in northern Mexico. From 2010 to 2013, couples underwent behavioral and biological assessments biannually for 24 months. Among 413 initially HIV-uninfected participants, 8 seroconverted during follow-up. Incidence of HIV (1.12 cases/100 person-years (PY)), chlamydia (9.47 cases/100 PY), active syphilis (4.01 cases/100 PY), and gonorrhea (1.78 cases/100 PY) was higher among women than among men (HIV: P = 0.069; all STIs combined: P < 0.001). In multivariable conditional logistic regression with individual fixed effects and correlated error terms within couples, risk of STI acquisition was significantly higher among women who had recently used cocaine, crack, or methamphetamine (adjusted odds ratio (OR) = 2.13, 95% confidence interval (CI): 1.07, 4.28). STI risk was lower among women who reported physically assaulting their male partners (adjusted OR = 0.44, 95% CI: 0.22, 0.86) and among men whose female partners had regular sex-work clients (adjusted OR = 0.38, 95% CI: 0.14, 1.03). Improving vulnerable couples' sexual health will require addressing the contexts in which drug use, interpersonal conflict, and economic vulnerability converge.

A network-level explanation for the differences in HIV prevalence in South Africa's racial groups

Analyses of individual-level risk factors have not been able to adequately explain why HIV has spread so extensively in southern Africa and why this has occurred especially within certain racial or ethnic groups. Using data from a longitudinal study of a representative sample of adolescents aged 14-22 living in Cape Town, South Africa, this article presents evidence of how differences in individual-level risk factors as well as sexual network structures between different racial or ethnic groups may help explain the differential spread of HIV in South Africa. Particular emphasis is placed on how levels of partner concurrency, respondent concurrency, mutual concurrency, serial concurrency and numbers of sexual partners and an average early age of sexual debut combine in different ways in the different racial or ethnic groups to create networks of sexual partnerships that differ in the density of their interconnections and hence potential for HIV spread. These network-level differences offer a potential explanation for the observed generalised HIV epidemic seen among the population of black South Africans.

Why do some South African ethnic groups have very high HIV rates and others not?

The differences in HIV prevalence between South Africa's racial/ethnic groups (19.9%, 3.2%, and 0.5% among 15-49-year-old blacks, coloureds and whites, respectively) are as big as those between the countries with the highest and lowest levels of HIV prevalence worldwide. These large racial/ethnic differences are largely determined by different sexual network structures. In networks among black South Africans, sexual partnerships are more likely to be arranged concurrently - a configuration that leads to exponential increases in the spread of HIV. An examination of the historical origins of polygamy (where it is normative for partnerships to be arranged concurrently) and monogamy (serial or lifetime) reveals that it is the practice of universal monogamy in stratified societies which is the outlier. The ideology and practice of universal monogamy originated in Europe as the result of several factors, most prominently conflicts between the Christian Church and the nobility. After its imposition in Europe, the European colonial project would see this ideology disseminated around the world. Under the influence of liberalism it would mutate into a secular and unacknowledged value-programme of monogamy as a universal norm. This value-programme and practice of monogamy (mostly serial) is still the norm for white South Africans; thus, this sexual behaviour 'spandrel' (by-product of other historical processes) is a large contributor to the lower levels of HIV prevalence among whites. In pre-colonial African societies, polygyny was normative, and the Christian value-programme of monogamy never achieved the hegemonic status it did in Europe and other areas of conquest. Married black African men who converted to Christianity were no less likely to have additional sexual partners, but only more likely to conceal them. The ongoing secrecy about having concurrent partners has contributed to the connectedness of sexual networks among black Africans at large and in this manner has contributed to the rapid spread of HIV.

HIV estimates at second subnational level from national population-based surveys

Objectives:

A better understanding of the subnational variations could be paramount to the efficiency and effectiveness of the response to the HIV epidemic. The purpose of this study is to describe the methodology used to produce the first estimates at second subnational level released by UNAIDS.

Methods:

We selected national population-based surveys with HIV testing and survey clusters geolocation, conducted in 2008 or later. A kernel density estimation approach (prevR) with adaptive bandwidths was used to generate a surface of HIV prevalence. This surface was combined with LandScan global population distribution grid to estimate the spatial distribution of people living with HIV (PLWHIV). Finally, results were adjusted to national UNAIDS's published estimates and merged per second subnational administrative unit. An indicator of the quality of the estimates was computed for each administrative unit.

Results:

These estimates combine two complementary approaches: the prevR method, focusing on spatial variations of HIV prevalence, as well as national estimates published by UNAIDS, taking into account trends of HIV prevalence over time. Seventeen country reports have been produced. However, quality of the estimates at second subnational level is highly heterogonous between countries, depending on the number of units and the survey sampling size. In some countries, estimates at second subnational level are very uncertain and should be interpreted with caution.

Conclusion:

These estimates at second subnational level constitute a first step to help countries to better understand their HIV epidemic and to inform programming at lower geographical levels. Further developments are needed to better match local needs.

No association between gender inequality and peak HIV prevalence in developing countries - an ecological study

The prevalence of both gender inequality and HIV prevalence vary considerably both within all developing countries and within those in sub-Saharan Africa. We test the hypothesis that the extent of gender inequality is associated with national peak HIV prevalence. Linear regression was used to test the association between national peak HIV prevalence and three markers of gender equality - the gender-related development index (GDI), the gender empowerment measure (GEM), and the gender inequality index (GII). No evidence was found of a positive relationship between gender inequality and HIV prevalence, either in the analyses of all developing countries or those limited to Africa. In the bivariate analyses limited to Africa, there was a positive association between the two measures of gender "equality" and peak HIV prevalence (GDI: coefficient 28, 95% confidence interval (CI) 9.1-46.8; GEM: coefficient 54.8, 95% CI 20.5-89.1). There was also a negative association between the marker of gender "inequality" and peak HIV prevalence (GII: coefficient -66.9, 95% CI -112.8 to -21.0). These associations all disappeared on multivariate analyses. We could not find any evidence to support the hypothesis that variations in the extent of gender inequality explain variations in HIV prevalence in developing countries.

Evidence for localised HIV related micro-epidemics associated with the decentralised provision of antiretroviral treatment in rural South Africa: a spatio-temporal analysis of changing mortality patterns (2007-2010)

Background

In this study we analysed the spatial and temporal changes in patterns of mortality over a period when antiretroviral therapy (ART) was rolled out in a rural region of north–eastern South Africa. Previous studies have identified localised concentrated HIV related sub–epidemics and recommended that micro–level analyses be carried out in order to direct focused interventions.

Methods

Data from an ongoing health and socio–demographic surveillance study was used in the analysis. The follow–up was divided into two periods, 2007–2008 and 2009–2010, representing the times immediately before and after the effects on mortality of the decentralised ART provision from a newly established local health centre would be expected to be evident. The study population at the start of the analysis was approximately 73 000 individuals. Data were aggregated by village and also using a 2 × 2 km grid. We identified villages, grid squares and regions in the site where mortality rates within each time period or rate ratios between the periods differed significantly from the overall trends. We used clustering techniques to identify cause–specific mortality hotspots.

Findings

Comparing the two periods, there was a 30% decrease in age and gender standardised adult HIV–related and TB (HIV/TB) mortality with no change in mortality due to other causes. There was considerable spatial heterogeneity in the mortality patterns. Areas separated by 2 to 4 km with very different epidemic trajectories were identified. There was evidence that the impact of ART in reducing HIV/TB mortality was greatest in communities with higher mortality rates in the earlier period.

Conclusions

This study shows the value of conducting high resolution spatial analyses in order to understand how local micro–epidemics contribute to changes seen over a wider area. Such analyses can support targeted interventions.

Piloting a 'spatial isolation' index: the built environment and sexual and drug use risks to sex workers

BACKGROUND

Employing innovative mapping and spatial analyses of individual and neighbourhood environment data, we examined the social, physical and structural features of overlapping street-based sex work and drug scenes and explored the utility of a 'spatial isolation index' in explaining exchanging sex for drugs and exchanging sex while high.

METHODS

Analyses drew on baseline interview and geographic data (January 2010-October 2011) from a large prospective cohort of street and off-street sex workers (SWs) in Metropolitan Vancouver and external publically-available, neighbourhood environment data. An index measuring 'spatial isolation' was developed from seven indicators measuring features of the built environment within 50m buffers (e.g., industrial or commercial zoning, lighting) surrounding sex work environments. Bivariate and multivariable logistic regression was used to examine associations between the two outcomes (exchanged sex for drugs; exchanged sex while high) and the index, as well as each individual indicator.

RESULTS

Of 510 SWs, 328 worked in street-based/outdoor environments (e.g., streets, parks, alleys) and were included in the analyses. In multivariable analysis, increased spatial isolation surrounding street-based/outdoor SWs' main places of servicing clients as measured with the index was significantly associated with exchanging sex for drugs. Exchanging sex for drugs was also significantly positively associated with an indicator of the built environment suggesting greater spatial isolation (increased percent of parks) and negatively associated with those suggesting decreased spatial isolation (increased percent commercial areas, increased count of lighting, increased building footprint). Exchanging sex while high was negatively associated with increased percent of commercial zones but this association was removed when adjusting for police harassment.

CONCLUSIONS

The results from our exploratory study highlight how built environment shapes risks within overlapping street-based sex work and drug scenes through the development of a novel index comprised of multiple indicators of the built environment available through publicly available data, This study informs the important role that spatially-oriented responses, such as safer-environment interventions, and structural responses, such as decriminalization of sex work can play in improving the health, safety and well-being of SWs.

The global epidemiology of bacterial vaginosis: a systematic review

Bacterial vaginosis (BV) enhances the acquisition and transmission of a range of sexually transmitted infections including human immunodeficiency virus. This has made it more important to uncover the reasons why some populations have very high BV prevalences and others not. This systematic review describes the global epidemiology of BV. It summarizes data from peer-reviewed publications detailing the population prevalence of BV as diagnosed by a standardized and reproducible methodology-Nugent scoring system. BV variations between countries, and between ethnic groups within countries, are described. We evaluated 1692 English- and non-English-language articles describing the prevalence of BV using MEDLINE and the Web of Science databases. A total of 86 articles met our inclusion criteria. BV prevalences were found to vary considerably between ethnic groups in North America, South America, Europe, the Middle East, and Asia. Although BV prevalence is, in general, highest in parts of Africa and lowest in much of Asia and Europe, some populations in Africa have very low BV prevalences and some in Asia and Europe have high rates.

Sexual risk behaviours and barriers to HIV testing among clients of female sex workers in Guatemala: a qualitative study

Few interventions have targeted clients of female sex workers in Central America, despite their potential role in HIV/STI prevention. Semi-structured interviews were conducted with 30 clients of female sex workers on attitudes towards prevention of HIV/STIs, barriers to condom use and behaviour towards HIV/STI testing and treatment in Escuintla, Guatemala. Despite high knowledge of condoms as an HIV/STI preventive measure, the decision to use them was often based on the client's social judgment of the woman's sexual conduct. Regular clients reported lower condom use. Clients' risk perception diminished with the awareness of the public HIV/STI clinic addressed to female sex workers. Most preferred private clinics to increase confidentiality and were reluctant to take the HIV test for fear of a positive result. Outreach programmes offering HIV/STI counselling and testing to clients of female sex workers could increase their test uptake and health-seeking behaviour and reduce potential transmission to the general population.

HIV prevention, structural change and social values: the need for an explicit normative approach

BACKGROUND

The fact that HIV prevention often deals with politicised sexual and drug taking behaviour is well known, but structural HIV prevention interventions in particular can involve alteration of social arrangements over which there may be further contested values at stake. As such, normative frameworks are required to inform HIV prevention decisions and avoid conflicts between social goals.

METHODS

This paper provides a conceptual review and discussion of the normative issues surrounding structural HIV prevention strategies. It applies political and ethical concepts to explore the contested nature of HIV planning and suggests conceptual frameworks to inform future structural HIV responses.

RESULTS

HIV prevention is an activity that cannot be pursued without making value judgements; it is inherently political. Appeals to health outcomes alone are insufficient when intervention strategies have broader social impacts, or when incidence reduction can be achieved at the expense of other social values such as freedom, equality, or economic growth. This is illustrated by the widespread unacceptability of forced isolation which may be efficacious in preventing spread of infectious agents, but conflicts with other social values.

CONCLUSIONS

While no universal value system exists, the capability approach provides one potential framework to help overcome seeming contradictions or value trade-offs in structural HIV prevention approaches. However, even within the capability approach, valuations must still be made. Making normative values explicit in decision making processes is required to ensure transparency, accountability, and representativeness of the public interest, while ensuring structural HIV prevention efforts align with broader social development goals as well.

Increasing access and ownership of clinical services at an HIV prevention project for sex workers in Mysore, India

Increasing sex workers' (SWs) access to and utilisation of health care services is a key part of HIV prevention. An HIV prevention project in Mysore, India, has been particularly successful in fostering a new norm of health care seeking among local SWs while facilitating community ownership of health care delivery. This paper describes how the use of occupational health ideologies, along with the creation of enabling environments, facilitated the uptake of project healthcare services and transformed power relationships between SWs and their healthcare providers. These changes led Mysore's SWs to initiate health-enhancing actions that moved beyond project imperatives to serve self-identified community needs.

Chlamydia positivity in women screened in family planning clinics: racial/ethnic differences and trends in the northwest U.S., 1997-2006

OBJECTIVES

We assessed chlamydia trends, individual-level risk factors, and population-level area-based socioeconomic measures (ABSMs) associated with chlamydia infection in women attending U.S. Public Health Service (PHS) Region X Infertility Prevention Project (IPP) family planning (FP) clinics from 1997-2006. We then explored these measures within racial/ethnic subpopulations.

METHODS

Using data from 667,223 chlamydia tests obtained from women aged 15-24 years screened in 201 FP clinics, we employed a generalized mixed model with logistic link, incorporating clinic and ZIP code as random effects to adjust for risk of chlamydia associated with individual- and population-level (areal) measures for the overall population and for each racial/ethnic subpopulation.

RESULTS

Significant racial/ethnic differences in chlamydia persisted after adjusting for individual and aggregate factors. Relatively steep chlamydia gradients were found across racial/ethnic ABSM levels. Compared with white women, infection risk was significantly higher for black (adjusted odds ratio [AOR] = 1.93), American Indian/Alaska Native (AOR=1.62), Asian/Pacific Islander (AOR=1.42), and Hispanic (AOR=1.28) women. The impact of population-level ABSMs on chlamydia varied across racial/ethnic groups and was generally modest. Among white women, there was a significant 4% relative annual increase in predicted chlamydia during the 10-year period 1997-2006. Chlamydia positivity over time did not change for racial/ethnic minority groups after adjusting for individual- and population-level factors.

CONCLUSIONS

Racial/ethnic differences in chlamydia persisted over time and were not mitigated by adjustment for aggregate socioeconomic position or areal racial/ethnic measures. Changes in project strategies will be needed to address racial/ethnic disparities for chlamydial infection among young female FP clinic clients.

Incorporating geospatial capacity within clinical data systems to address social determinants of health

Linking electronic health record (EHR) systems with community information systems (CIS) holds great promise for addressing inequities in social determinants of health (SDH). While EHRs are rich in location-specific data that allow us to uncover geographic inequities in health outcomes, CIS are rich in data that allow us to describe community-level characteristics relating to health. When meaningfully integrated, these data systems enable clinicians, researchers, and public health professionals to actively address the social etiologies of health disparities.This article describes a process for exploring SDH by geocoding and integrating EHR data with a comprehensive CIS covering a large metropolitan area. Because the systems were initially designed for different purposes and had different teams of experts involved in their development, integrating them presents challenges that require multidisciplinary expertise in informatics, geography, public health, and medicine. We identify these challenges and the means of addressing them and discuss the significance of the project as a model for similar projects.

Partner Concurrency and the STD/HIV Epidemic

Conceptually and theoretically, it is easy to see how short gaps and concurrent partnerships fuel the spread of sexually transmitted infections (STI) and HIV in populations. The consequences of concurrency are bounded by the duration of the infectious period and by the relationships between concurrent partnerships and other dimensions of sexual behavior. Consequently, it is difficult to predict how concurrent partnerships or short gaps may be related to the spread of STI and HIV in a particular epidemiologic context in empirical reality. In recent years, analyses of sexual behavior data collected through nationally representative surveys revealed similar prevalences of concurrent sexual partnerships in Western populations. The association between concurrent sexual partnerships and STI/HIV risk is complicated. At the population level, recent findings suggest that the ecological association between polygyny and HIV prevalence is negative at the country level and at the sub-national level. To address the need for agreed-upon standard definitions and measures of concurrent sexual partnerships, which will facilitate comparisons across time and settings, the Joint United Nations Program on HIV/AIDS (UNAIDS) Reference Group on Estimates, Modelling, and Projections convened a meeting in April 2009. The recommendations developed at this meeting include suggestions for a definition, indicators, and measures of concurrency.

Neighborhood environment, sexual risk behaviors and acquisition of sexually transmitted infections among adolescents diagnosed with psychological disorders

The association between neighborhood environment and prevalence of STIs, sexual partner variables and condom use among adolescents with psychological disorders was examined. Cross-sectional data in three urban areas of the US (Southeast, Northeast and Midwest) were obtained from 384 sexually active male and female participants who provided urine samples for laboratory-confirmed testing of Neisseria gonorrhoeae, Chlamydia trachomatis and Trichomonas vaginalis. A total of 15.4% of participants tested positive for one of the three STIs. Results indicated that relative to adolescents living in low risk neighborhood environments, those living in high risk environments were significantly more likely to have a STI and to report having casual partners. Findings suggest that in high risk neighborhoods, STI acquisition may be less dependent on condom use and more dependent on other contextual factors. The importance of expanding public health research to include assessment of neighborhood context as a determinant of sexual risk-taking is emphasized.

Determinants of HIV-1 transmission in men who have sex with men: a combined clinical, epidemiological and phylogenetic approach

OBJECTIVES

To identify biological factors associated with HIV transmission in men who have sex with men (MSM).

DESIGN

A longitudinal phylogenetic analysis of HIV-1 from an MSM cohort, incorporating clinical and epidemiological data.

METHODS

Potential individuals were HIV-infected MSM attending a sexual health clinic between 2000 and 2006. Individuals were classified such that they could move from recent to chronic infection categories. HIV-1pol gene sequences were obtained from plasma virus or proviral DNA and clusters estimated by maximum likelihood and conservative genetic distance differences. The single most likely transmitter generating each recent infection was ascertained and risk factors around time of likely transmission explored using Poisson regression modelling.

RESULTS

Out of 1144 HIV-infected MSM, pol sequence data were obtained for 859 (75%); 159 out of 859 (19%) were recently HIV infected at diagnosis. A single most likely transmitter was identified for 41 out of 159 (26%), of which 11 were recently infected (27%) and 30 chronically infected. Factors associated with transmission in multivariable analysis were: younger age {rate ratio per 5 years older 0.68 [95% confidence interval (CI) 0.54-0.86], P=0.0009}, higher viral load [rate ratio per log higher 1.61 (95% CI 1.15-2.25), P=0.005], recent infection [rate ratio 3.88 (95% CI 1.76-8.55), P=0.0008] and recent sexually transmitted disease [rate ratio 5.32 (95% CI 2.51-11.29), P=0.0001]. HAART was highly protective in a univariable model, RR 0.14 (95% CI 0.07-0.27, P=0.0001).

CONCLUSION

Onward transmission of HIV among MSM is significantly associated with recent infection, sexually transmitted diseases and higher viral load, and reduced by effective HAART. The majority of new infections appear to occur from individuals whose infection was undiagnosed at the time of transmission.

An ecological approach to addressing HIV/AIDS in the African American community

The disproportionate impact of HIV/AIDS on African Americans is a significant public health challenge. The complex constellation of individual, social, and environmental factors influencing transmission, require ecological solutions that recognize these multiple levels of influence and actively involve communities. This article describes the formation of a community-based coalition and highlights three initiatives it has undertaken in the areas of mobile HIV testing, HIV education, and faith-based work to improve HIV services for African Americans.

Rethinking the role of the local community in HIV epidemic spread in sub-Saharan Africa: a proximate-determinants approach

The spread of HIV in sub-Saharan Africa continues largely unabated. To improve prevention interventions, a better understanding of the determinants of HIV infection is required. Conceptual frameworks can guide epidemiological investigation and prevent a misguided focus on single risk factors in isolation. Existing frameworks of HIV infection focus on transmission. However, the transmitting individual is rarely known. By contrast, data on individual HIV acquisition are available from longitudinal studies and tests for recent HIV infection. From the perspective of individuals susceptible to HIV, it is important to distinguish between factors determining the individual's biological disposition and sexual behavior and community-level factors, which can affect both HIV acquisition and the likelihood that a sex partner chosen from a community will be infected with HIV and transmit the infection. We propose a framework that takes the susceptible individual as a starting point and links distal, proximate and biological determinants of HIV infection at both the individual and the community level. We describe three necessary ingredients for the use of the framework (identification of the relevant community, multilevel analysis and methods for causal inference).

Localized spatial clustering of HIV infections in a widely disseminated rural South African epidemic

BACKGROUND

South Africa contains more than one in seven of the world's HIV-positive population. Knowledge of local variation in levels of HIV infection is important for prioritization of areas for intervention. We apply two spatial analytical techniques to investigate the micro-geographical patterns and clustering of HIV infections in a high prevalence, rural population in KwaZulu-Natal, South Africa.

METHODS

All 12,221 participants who consented to an HIV test in a population under continuous demographical surveillance were linked to their homesteads and geo-located in a geographical information system (accuracy of <2 m). We then used a two-dimensional Gaussian kernel of radius 3 km to produce robust estimates of HIV prevalence that vary across continuous geographical space. We also applied a Kulldorff spatial scan statistic (Bernoulli model) to formally identify clusters of infections (P < 0.05).

RESULTS

The results reveal considerable geographical variation in local HIV prevalence (range = 6-36%) within this relatively homogenous population and provide clear empirical evidence for the localized clustering of HIV infections. Three high-risk, overlapping spatial clusters [Relative Risk (RR) = 1.34-1.62] were identified by the Kulldorff statistic along the National Road (P < or = 0.01), whereas three low risk clusters (RR = 0.2-0.38) were identified elsewhere in the study area (P < or = 0.017).

CONCLUSIONS

The findings show the existence of several localized HIV epidemics of varying intensity that are partly contained within geographically defined communities. Despite the overall high prevalence of HIV in many rural South African settings, the results support the need for interventions that target socio-geographic spaces (communities) at greatest risk to supplement measures aimed at the general population.

Phenotypic and genotypic characterization of Neisseria gonorrhoeae in parts of Italy: detection of a multiresistant cluster circulating in a heterosexual network

Data concerning Neisseria gonorrhoeae infections in Italy are scarce, and there is little information on the phenotypic and genotypic characteristics of the circulating strains. In this study, 326 isolates collected from 397 patients, with or without concurrent human immunodeficiency virus (HIV) infection, were cultured and characterized by serovar and antimicrobial susceptibility to five antimicrobials. N. gonorrhoeae multi-antigen sequence typing (NG-MAST) was also performed for strain characterization and to identify a transmission network. Gonococcal infection was diagnosed in 364 males and 33 females, 296 of whom were Italian and 96 of whom were foreigners (nationality was unknown in five cases). Among the 364 males, 197 were heterosexual, and the median age was 31 years. Approximately 8.3% of all the investigated patients were HIV-1-positive. The isolates were assigned to three different serovars (IA, IB, IA/IB), IB being the most frequently encountered. A significant rate of resistant gonococci was also observed; 34%, 25.5% and 19.1% of ciprofloxacin-resistant, penicillin-resistant and tetracycline-resistant phenotypes, respectively, were detected, and 10.2% of strains were multidrug-resistant. Together with the presence of different sequence types (STs), identified by NG-MAST, a multidrug-resistant cluster, ST661, was detected in a heterosexual network in a precise geographical area of the country. In particular, all strains belonging to ST661 showed identical profiles according to pulsed-field gel electrophoresis (PFGE), all were serotype IB, and all were resistant to penicillin, ciprofloxacin and tetracycline.

The SEEDs of two gastrointestinal diseases: socioeconomic, environmental, and demographic factors related to cryptosporidiosis and giardiasis in Massachusetts

OBJECTIVES

We assessed associations between community-level socioeconomic, demographic, and environmental characteristics, and the presence of two potentially waterborne infectious diseases, cryptosporidiosis and giardiasis, as reported to the Massachusetts Department of Public Health.

METHODS

We created a series of maps showing the spatial distribution of cryptosporidiosis and giardiasis in Massachusetts (1993-2002) overall and by age, using logistic regression to analyze associations between community-level characteristics and the presence of at least one reported case of each disease. This analysis was repeated for communities with predominantly private water supplies.

RESULT

After adjusting for population size, higher population density and larger than average household sizes were associated with increased odds of reported cases of cryptosporidiosis. Giardiasis was also associated with high population density, but was not associated with household size. In the elderly, income was positively associated with the presence of giardiasis.

DISCUSSION

These findings suggest that greater population density and larger household sizes may increase the likelihood of protozoan gastrointestinal infection. The results emphasize the necessity to account for distal factors, such as demographic characteristics, that may ultimately play a role in the transmission or reporting of disease.

Infectious syphilis in high-income settings in the 21st century

In high-income countries after World War II, the widespread availability of effective antimicrobial therapy, combined with expanded screening, diagnosis, and treatment programmes, resulted in a substantial decline in the incidence of syphilis. However, by the turn of the 21st century, outbreaks of syphilis began to occur in different subpopulations, especially in communities of men who have sex with men. The reasons for these outbreaks include changing sexual and social norms, interactions with increasingly prevalent HIV infection, substance abuse, global travel and migration, and underinvestment in public-health services. Recently, it has been suggested that these outbreaks could be the result of an interaction of the pathogen with natural immunity, and that syphilis epidemics should be expected to intrinsically cycle. We discuss this hypothesis by examining long-term data sets of syphilis. Today, syphilis in western Europe and the USA is characterised by low-level endemicity with concentration among population subgroups with high rates of partner change, poor access to health services, social marginalisation, or low socioeconomic status.

Sexually transmitted infections in Western Europe among HIV-positive men who have sex with men

BACKGROUND

Since 1996, there has been a resurgence in sexually transmitted infections (STIs) among men who have sex with men (MSM) in Western Europe. This has coincided with a significant decrease in HIV-associated mortality following the introduction of highly active antiretroviral therapies (HAART) and a corresponding increase in the number of MSM living with HIV. Levels of unprotected anal intercourse have also increased. In this article, we use STI surveillance data from a number of Western European countries to better understand the contribution of HIV-positive MSM to the recent increase in STIs.

METHODS

Published literature, surveillance reports, and ad hoc publications relating to HIV prevalence trends and STIs among HIV-positive MSM in Western Europe were reviewed.

RESULTS

Post-HAART, HIV prevalence among community samples of MSM ranged from 5% to 18%. HIV prevalence among MSM diagnosed with an STI was substantially higher. On average, HIV prevalence among MSM diagnosed with syphilis in 11 countries was 42% (range 14%-59%). Most HIV-positive MSM with syphilis were aware of their HIV status. In England and Wales, 32% of MSM with gonorrhea were HIV-positive in 2004. Outbreaks of lymphogranuloma venereum have been documented in 9 countries; HIV-positive MSM accounted for 75% of cases on average (range 0%-92%). Cases of sexually transmitted hepatitis C have been predominantly identified among HIV-positive MSM in Rotterdam, Paris, Amsterdam, and the United Kingdom.

CONCLUSIONS

In Western Europe, STIs have been disproportionately diagnosed among HIV-positive MSM post-HAART. Improved survival coupled with serosorting among HIV-positive MSM appears to explain the high prevalence of HIV among MSM with STIs. STI transmission among HIV-positive men will have contributed substantially to increasing STI trends seen among MSM in Western Europe, since 1996. These findings highlight the need for routine STI testing among HIV-positive MSM as well as safer sex messages highlighting the implications of STI coinfection.

Blind spots in the epidemiology of HIV in black Americans

In the USA, annual rates of new human immunodeficiency virus (HIV)/AIDS diagnoses are seven and 21 times higher in black men and women, respectively, than in whites. Epidemiological inquiry on this disparity has chiefly focused on contextual factors; such emphasis has eclipsed study of direct HIV vectors. The US Centers for Disease Control and Prevention recently announced its intention to curb HIV propagation in black communities, recommending culturally appropriate HIV/AIDS strategies. Contemplated societal interventions should be informed by data evaluating more direct (and under-assessed) HIV transmission vectors, specifically anal intercourse and unsuspected blood exposures. This recommendation involves tracing sexual and non-sexual contacts of recently infected persons and uninfected controls, coupled with DNA sequencing of HIV isolates. Public health authorities do not know the extent to which unmeasured yet plausible HIV transmission vectors can account for ethnic disparities. Appropriate prevention strategies depend critically on direct, rather than ecologic, evidence.

The future of HIV prevention: control of sexually transmitted infections and circumcision interventions

Prevention and control of sexually transmitted infections (STIs) has proven effective in reducing HIV infection when treatment is available promptly for symptomatic persons in conditions of an emerging epidemic. Biologically, it is assumed that reduced genital tract inflammation reduces infectiousness for HIV as well as reducing susceptibility in HIV-uninfected persons. Male circumcision has been demonstrated effective in reducing risk for HIV infection in three separate trials from South Africa, Kenya, and Uganda. Global expansion of STI treatment and male circumcision programs are vital tools for control of HIV infection; current evidence is reviewed and research priorities are presented.

Expansion of HIV/AIDS in China: lessons from Yunnan Province

In this article we systematically and critically review the Chinese and English language literature on human immunodeficiency virus (HIV)-related studies in Yunnan Province, Southwestern China. Yunnan Province had the first Chinese HIV outbreak and is still the worst affected area in the nation. Since 1989, HIV infection has extended from injecting drug users into the general population through sexual transmission. Since the economic reform of the 1980s, changed social norms and increased migration have spawned increases in HIV-related risk behaviors such as drug use and commercial sex work. A smaller size of "bridge" populations and lower sexual contact rates between persons in "bridge" and general populations may explain the slower expansion of the HIV epidemic in Yunnan compared to nearby Southeast Asian nations. In 2004, women in antenatal care had a 0.38% HIV prevalence province wide, although >1% infection rates are seen in those counties with high injection drug rates. Patterns of drug trafficking have spread the unusual recombinant HIV subtypes first seen in Yunnan to far-flung regions of China. Increased efforts of Yunnan's HIV control program are correlated with an improved general HIV awareness, but risk behaviors continue at worrisome rates. Future efforts should focus on changing risk behaviors, including harm reduction and condom promotion, especially among the "bridge" groups. The resurgence of commercial sex work in Yunnan, and the high frequency of workers migrating into provinces far from home and family are all sociocultural factors of considerable importance for future HIV and sexually transmitted disease control in China.

Population contextual associations with heterosexual partner numbers: a multilevel analysis

OBJECTIVE

The study examines whether an individual's sexual behaviour is associated with the demographic context within which they live.

METHODS

Data from a large behavioural survey were matched to the census and the number of opposite sex partners individuals reported having in the year before interview was modelled against a suite of individual characteristics and analogous characteristics for the population in which they lived.

RESULTS

The number of partners reported (none, one, two, three, or more) were variously associated with an individual's gender, age, marital status, sexual identity, and same sex activity in the previous year. Additionally, population age structure, sex ratio, and the proportion of the population reporting specific patterns of sexual activity were associated with the behaviour of individuals.

CONCLUSIONS

This study demonstrates that population context is associated with individual behaviour even after individual characteristics have been taken into account. This suggests that multilevel modelling of sexual behaviour data can provide new insights into the pattern of sexual behaviour.